Taiwan Patent Publication No. 399348 discloses a method for preparing a bipolar plate, which comprises: mixing at least an electrically conductive material, at least a resin, and at least a hydrophilic agent suitable for a proton exchange membrane fuel cell, to form a substantially homogeneous mixture wherein, based on the weight of said mixture, said at least an electrically conductive material is about 50% to about 95% and said at least a resin is about 5%; and molding said mixture to form a bipolar plate with a desired shape at a temperature of about 250° C. to about 500° C. and a pressure of about 500 psi to about 4000 psi, wherein said at least a resin is selected from the group consisting of thermosetting resins, thermoplastic resins, and a mixture thereof, and said at least an electrically conductive material is selected from the group consisting of graphite, carbon black, carbon fiber, and a mixture thereof.
U.S. Pat. No. 6,248,467 discloses a fuel cell composite bipolar plate, wherein the particle size of the graphite powder is mainly in the range of 80 mesh–325 mesh. This patent has mentioned that the mixing of the resin becomes inhomogeneous during processing when the particle size of the graphite powder is larger than 150 μm.
WO 00/57506 discloses a highly conductive molding composition for molding a fuel cell bipolar plate, wherein the particle size of the graphite powder used is mainly in the range of 44 μm to 150 μm, wherein the amount of the graphite powder larger than 150 μm needs to be lower than 10%, and the amount of the graphite powder smaller than 44 μm also needs to be lower than 10%.
To this date, the industry is still continuously looking for a fuel cell bipolar plate having a high electric conductivity, excellent mechanical properties, and a high thermal stability.